[WIP] Add support for PEP 751 pylock.toml files in backends

[Copilot]

Thanks for asking me to work on this. I will get started on it and keep this PR's description up to date as I form a plan and make progress.

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This section details on the original issue you should resolve

<issue_title>support PEP 751 pylock.toml files in backends</issue_title>
<issue_description>What's the problem this feature will solve?

Installing/running package in an isolated environment will be more reproducible (with exact dependencies versions as used when packaging), if the package source includes pylock.toml format.
I think this would be potentially desired in a case of an isolated environment for one tool.

PEP 578 introduced a new common dependency locking format, and it recently gets supported in other tools - pip (currently experimental), uv.

Describe the solution you'd like

If the package contains pylock.toml file, then some equivalent solution could be used for:
pip - use pip install -r pylock.toml first to install dependencies, then install the package
uv - similar uv pip sync pylock.toml

pip support is currently experimental, it may wait until it gets out of this stage.

I guess this is more for a discussion on potential implementation.</issue_description>

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